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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Typically, asteroids — like the one depicted in this artist’s concept — originate from the main asteroid belt between the orbits of Mars and Jupiter, but a small population of near-Earth objects may also come from the Moon’s surface after being ejected into space by an impact.NASA/JPL-Caltech The near-Earth object was likely ejected into space after an impact thousands of years ago. Now it could contribute new insights to asteroid and lunar science.
The small near-Earth object 2024 PT5 captured the world’s attention last year after a NASA-funded telescope discovered it lingering close to, but never orbiting, our planet for several months. The asteroid, which is about 33 feet (10 meters) wide, does not pose a hazard to Earth, but its orbit around the Sun closely matches that of our planet, hinting that it may have originated nearby.
As described in a study published Jan. 14 in the Astrophysical Journal Letters, researchers have collected further evidence of 2024 PT5 being of local origin: It appears to be composed of rock broken off from the Moon’s surface and ejected into space after a large impact.
“We had a general idea that this asteroid may have come from the Moon, but the smoking gun was when we found out that it was rich in silicate minerals — not the kind that are seen on asteroids but those that have been found in lunar rock samples,” said Teddy Kareta, an astronomer at Lowell Observatory in Arizona, who led the research. “It looks like it hasn’t been in space for very long, maybe just a few thousand years or so, as there’s a lack of space weathering that would have caused its spectrum to redden.”
The asteroid was first detected on Aug. 7, 2024, by the NASA-funded Sutherland, South Africa, telescope of the University of Hawai’i’s Asteroid Terrestrial-impact Last Alert System (ATLAS). Kareta’s team then used observations from the Lowell Discovery Telescope and the NASA Infrared Telescope Facility (IRTF) at the Mauna Kea Observatory in Hawai’i to show that the spectrum of reflected sunlight from the small object’s surface didn’t match that of any known asteroid type; instead, the reflected light more closely matched rock from the Moon.
Not (Old) Rocket Science
A second clue came from observing how the object moves. Along with asteroids, Space Age debris, such as old rockets from historic launches, can also be found in Earth-like orbits.
The difference in their orbits has to do with how each type responds to solar radiation pressure, which comes from the momentum of photons — quantum particles of light from the Sun — exerting a tiny force when they hit a solid object in space. This momentum exchange from many photons over time can push an object around ever so slightly, speeding it up or slowing it down. While a human-made object, like a hollow rocket booster, will move like an empty tin can in the wind, a natural object, such as an asteroid, will be much less affected.
Researchers studying asteroid 2024 PT5 have plotted its looping motion on two graphs. To a trained eye, they show that the object never gets captured by Earth’s gravity but, instead, lingers nearby before continuing its orbit around the Sun. NASA/JPL-Caltech To rule out 2024 PT5 being space junk, scientists at NASA’s Center for Near Earth Object Studies (CNEOS), which is managed by the agency’s Jet Propulsion Laboratory in Southern California, analyzed its motion. Their precise calculations of the object’s motion under the force of gravity ultimately enabled them to search for additional motion caused by solar radiation pressure. In this case, the effects were found to be too small for the object to be artificial, proving 2024 PT5 is most likely of natural origin.
“Space debris and space rocks move slightly differently in space,” said Oscar Fuentes-Muñoz, a study coauthor and NASA postdoctoral fellow at JPL working with the CNEOS team. “Human-made debris is usually relatively light and gets pushed around by the pressure of sunlight. That 2024 PT5 doesn’t move this way indicates it is much denser than space debris.”
Asteroid Lunar Studies
The discovery of 2024 PT5 doubles the number of known asteroids thought to originate from the Moon. Asteroid 469219 Kamo’oalewa was found in 2016 with an Earth-like orbit around the Sun, indicating that it may also have been ejected from the lunar surface after a large impact. As telescopes become more sensitive to smaller asteroids, more potential Moon boulders will be discovered, creating an exciting opportunity not only for scientists studying a rare population of asteroids, but also for scientists studying the Moon.
If a lunar asteroid can be directly linked to a specific impact crater on the Moon, studying it could lend insights into cratering processes on the pockmarked lunar surface. Also, material from deep below the lunar surface — in the form of asteroids passing close to Earth — may be accessible to future scientists to study.
“This is a story about the Moon as told by asteroid scientists,” said Kareta. “It’s a rare situation where we’ve gone out to study an asteroid but then strayed into new territory in terms of the questions we can ask of 2024 PT5.”
The ATLAS, IRTF, and CNEOS projects are funded by NASA’s planetary defense program, which is managed by the Planetary Defense Coordination Office at NASA Headquarters in Washington.
For more information about asteroids and comets, visit:
https://www.jpl.nasa.gov/topics/asteroids/
NASA Asteroid Experts Create Hypothetical Impact Scenario for Exercise NASA Researchers Discover More Dark Comets Lesson Plan: How to Explore an Asteroid News Media Contacts
Ian J. O’Neill
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-2649
ian.j.oneill@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Kevin Schindler
Lowell Observatory Public Information Officer
928-607-1387
kevin@lowell.edu
2025-007
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Last Updated Jan 22, 2025 Related Terms
Asteroids Earth's Moon Jet Propulsion Laboratory Planetary Defense Planetary Defense Coordination Office Planetary Science Explore More
5 min read How New NASA, India Earth Satellite NISAR Will See Earth
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By NASA
NASA’s Jet Propulsion Laboratory used radar data taken by ESA’s Sentinel-1A satellite before and after the 2015 eruption of the Calbuco volcano in Chile to create this inter-ferogram showing land deformation. The color bands west of the volcano indicate land sinking. NISAR will produce similar images.ESA/NASA/JPL-Caltech A SAR image — like ones NISAR will produce — shows land cover on Mount Okmok on Alaska’s Umnak Island . Created with data taken in August 2011 by NASA’s UAVSAR instrument, it is an example of polarimetry, which measures return waves’ orientation relative to that of transmitted signals.NASA/JPL-Caltech Data from NASA’s Magellan spacecraft, which launched in 1989, was used to create this image of Crater Isabella, a 108-mile-wide (175-kilometer-wide) impact crater on Venus’ surface. NISAR will use the same basic SAR principles to measure properties and characteristics of Earth’s solid surfaces.NASA/JPL-Caltech Set to launch within a few months, NISAR will use a technique called synthetic aperture radar to produce incredibly detailed maps of surface change on our planet.
When NASA and the Indian Space Research Organization’s (ISRO) new Earth satellite NISAR (NASA-ISRO Synthetic Aperture Radar) launches in coming months, it will capture images of Earth’s surface so detailed they will show how much small plots of land and ice are moving, down to fractions of an inch. Imaging nearly all of Earth’s solid surfaces twice every 12 days, it will see the flex of Earth’s crust before and after natural disasters such as earthquakes; it will monitor the motion of glaciers and ice sheets; and it will track ecosystem changes, including forest growth and deforestation.
The mission’s extraordinary capabilities come from the technique noted in its name: synthetic aperture radar, or SAR. Pioneered by NASA for use in space, SAR combines multiple measurements, taken as a radar flies overhead, to sharpen the scene below. It works like conventional radar, which uses microwaves to detect distant surfaces and objects, but steps up the data processing to reveal properties and characteristics at high resolution.
To get such detail without SAR, radar satellites would need antennas too enormous to launch, much less operate. At 39 feet (12 meters) wide when deployed, NISAR’s radar antenna reflector is as wide as a city bus is long. Yet it would have to be 12 miles (19 kilometers) in diameter for the mission’s L-band instrument, using traditional radar techniques, to image pixels of Earth down to 30 feet (10 meters) across.
Synthetic aperture radar “allows us to refine things very accurately,” said Charles Elachi, who led NASA spaceborne SAR missions before serving as director of NASA’s Jet Propulsion Laboratory in Southern California from 2001 to 2016. “The NISAR mission will open a whole new realm to learn about our planet as a dynamic system.”
Data from NASA’s Magellan spacecraft, which launched in 1989, was used to create this image of Crater Isabella, a 108-mile-wide (175-kilometer-wide) impact crater on Venus’ surface. NISAR will use the same basic SAR principles to measure properties and characteristics of Earth’s solid surfaces.NASA/JPL-Caltech How SAR Works
Elachi arrived at JPL in 1971 after graduating from Caltech, joining a group of engineers developing a radar to study Venus’ surface. Then, as now, radar’s allure was simple: It could collect measurements day and night and see through clouds. The team’s work led to the Magellan mission to Venus in 1989 and several NASA space shuttle radar missions.
An orbiting radar operates on the same principles as one tracking planes at an airport. The spaceborne antenna emits microwave pulses toward Earth. When the pulses hit something — a volcanic cone, for example — they scatter. The antenna receives those signals that echo back to the instrument, which measures their strength, change in frequency, how long they took to return, and if they bounced off of multiple surfaces, such as buildings.
This information can help detect the presence of an object or surface, its distance away, and its speed, but the resolution is too low to generate a clear picture. First conceived at Goodyear Aircraft Corp. in 1952, SAR addresses that issue.
“It’s a technique to create high-resolution images from a low-resolution system,” said Paul Rosen, NISAR’s project scientist at JPL.
As the radar travels, its antenna continuously transmits microwaves and receives echoes from the surface. Because the instrument is moving relative to Earth, there are slight changes in frequency in the return signals. Called the Doppler shift, it’s the same effect that causes a siren’s pitch to rise as a fire engine approaches then fall as it departs.
Computer processing of those signals is like a camera lens redirecting and focusing light to produce a sharp photograph. With SAR, the spacecraft’s path forms the “lens,” and the processing adjusts for the Doppler shifts, allowing the echoes to be aggregated into a single, focused image.
Using SAR
One type of SAR-based visualization is an interferogram, a composite of two images taken at separate times that reveals the differences by measuring the change in the delay of echoes. Though they may look like modern art to the untrained eye, the multicolor concentric bands of interferograms show how far land surfaces have moved: The closer the bands, the greater the motion. Seismologists use these visualizations to measure land deformation from earthquakes.
Another type of SAR analysis, called polarimetry, measures the vertical or horizontal orientation of return waves relative to that of transmitted signals. Waves bouncing off linear structures like buildings tend to return in the same orientation, while those bouncing off irregular features, like tree canopies, return in another orientation. By mapping the differences and the strength of the return signals, researchers can identify an area’s land cover, which is useful for studying deforestation and flooding.
Such analyses are examples of ways NISAR will help researchers better understand processes that affect billions of lives.
“This mission packs in a wide range of science toward a common goal of studying our changing planet and the impacts of natural hazards,” said Deepak Putrevu, co-lead of the ISRO science team at the Space Applications Centre in Ahmedabad, India.
Learn more about NISAR at:
https://nisar.jpl.nasa.gov
News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
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Last Updated Jan 21, 2025 Related Terms
NISAR (NASA-ISRO Synthetic Aperture Radar) Earth Earth Science Earth Science Division Jet Propulsion Laboratory Explore More
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By European Space Agency
Image: This Copernicus Sentinel-2 image captures the borders between North and South Dakota and Minnesota blanketed with snow and ice. View the full article
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By NASA
NASA On April 21, 1972, NASA astronaut John W. Young, commander of the Apollo 16 mission, took a far-ultraviolet photo of Earth with an ultraviolet camera. Young’s original black-and-white picture was printed on Agfacontour professional film three times, with each exposure recording only one light level. The three light levels were then colored blue (dimmest), green (next brightest), and red (brightest), resulting in the enhanced-color image seen here.
Dr. George Carruthers, a scientist at the Naval Research Laboratory, developed the ultraviolet camera – the first Moon-based observatory – for Apollo 16. Apollo 16 astronauts placed the observatory on the Moon in April 1972, where it sits today on the Moon’s Descartes highland region, in the shadow of the lunar module Orion.
Image credit: NASA
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
An equal collaboration between NASA and the Indian Space Research Organisation, NISAR will offer unprecedented insights into Earth’s constantly changing land and ice surfaces using synthetic aperture radar technology. The spacecraft, depicted here in an artist’s concept, will launch from India.NASA/JPL-Caltech A Q&A with the lead U.S. scientist of the mission, which will track changes in everything from wetlands to ice sheets to infrastructure damaged by natural disasters.
The upcoming U.S.-India NISAR (NASA-ISRO Synthetic Aperture Radar) mission will observe Earth like no mission before, offering insights about our planet’s ever-changing surface.
The NISAR mission is a first-of-a-kind dual-band radar satellite that will measure land deformation from earthquakes, landslides, and volcanoes, producing data for science and disaster response. It will track how much glaciers and ice sheets are advancing or retreating and it will monitor growth and loss of forests and wetlands for insights on the global carbon cycle.
As diverse as NISAR’s impact will be, the mission’s winding path to launch — in a few months’ time — has also been remarkable. Paul Rosen, NISAR’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California, has been there at every step. He recently discussed the mission and what sets it apart.
NISAR Project Scientist Paul Rosen of NASA’s Jet Propulsion Laboratory first traveled to India in late 2011 to discuss collaboration with ISRO scientists on an Earth-observing radar mission. NASA and ISRO signed an agreement in 2014 to develop NISAR. NASA/JPL-Caltech How will NISAR improve our understanding of Earth?
The planet’s surfaces never stop changing — in some ways small and subtle, and in other ways monumental and sudden. With NISAR, we’ll measure that change roughly every week, with each pixel capturing an area about half the size of a tennis court. Taking imagery of nearly all Earth’s land and ice surfaces this frequently and at such a small scale — down to the centimeter — will help us put the pieces together into one coherent picture to create a story about the planet as a living system.
What sets NISAR apart from other Earth missions?
NISAR will be the first Earth-observing satellite with two kinds of radar — an L-band system with a 10-inch (25-centimeter) wavelength and an S-band system with a 4-inch (10-centimeter) wavelength.
Whether microwaves reflect or penetrate an object depends on their wavelength. Shorter wavelengths are more sensitive to smaller objects such as leaves and rough surfaces, whereas longer wavelengths are more reactive with larger structures like boulders and tree trunks.
So NISAR’s two radar signals will react differently to some features on Earth’s surface. By taking advantage of what each signal is or isn’t sensitive to, researchers can study a broader range of features than they could with either radar on its own, observing the same features with different wavelengths.
Is this new technology?
The concept of a spaceborne synthetic aperture radar, or SAR, studying Earth’s processes dates to the 1970s, when NASA launched Seasat. Though the mission lasted only a few months, it produced first-of-a-kind images that changed the remote-sensing landscape for decades to come.
It also drew me to JPL in 1981 as a college student: I spent two summers analyzing data from the mission. Seasat led to NASA’s Shuttle Imaging Radar program and later to the Shuttle Radar Topography Mission.
What will happen to the data from the mission?
Our data products will fit the needs of users across the mission’s science focus areas — ecosystems, cryosphere, and solid Earth — plus have many uses beyond basic research like soil-moisture and water resources monitoring.
We’ll make the data easily accessible. Given the volume of the data, NASA decided that it would be processed and stored in the cloud, where it’ll be free to access.
How did the ISRO partnership come about?
We proposed DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice), an L-band satellite, following the 2007 Decadal Survey by the National Academy of Sciences. At the time, ISRO was exploring launching an S-band satellite. The two science teams proposed a dual-band mission, and in 2014 NASA and ISRO agreed to partner on NISAR.
Since then, the agencies have been collaborating across more than 9,000 miles (14,500 kilometers) and 13 time zones. Hardware was built on different continents before being assembled in India to complete the satellite. It’s been a long journey — literally.
More About NISAR
The NISAR mission is an equal collaboration between NASA and ISRO and marks the first time the two agencies have cooperated on hardware development for an Earth-observing mission. Managed for the agency by Caltech, JPL leads the U.S. component of the project and is providing the mission’s L-band SAR. NASA is also providing the radar reflector antenna, the deployable boom, a high-rate communication subsystem for science data, GPS receivers, a solid-state recorder, and payload data subsystem.
Space Applications Centre Ahmedabad, ISRO’s lead center for payload development, is providing the mission’s S-band SAR instrument and is responsible for its calibration, data processing, and development of science algorithms to address the scientific goals of the mission. U R Rao Satellite Centre in Bengaluru, which leads the ISRO components of the mission, is providing the spacecraft bus. The launch vehicle is from ISRO’s Vikram Sarabhai Space Centre, launch services are through ISRO’s Satish Dhawan Space Centre, and satellite mission operations are by ISRO Telemetry Tracking and Command Network. National Remote Sensing Centre in Hyderabad is primarily responsible for S-band data reception, operational products generation, and dissemination.
To learn more about NISAR, visit:
https://nisar.jpl.nasa.gov
News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
2025-001
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Last Updated Jan 06, 2025 Related Terms
NISAR (NASA-ISRO Synthetic Aperture Radar) Climate Change Earth Earth Science Earth Science Division Ice & Glaciers Jet Propulsion Laboratory Seasat Shuttle Radar Topography Mission (SRTM) SIR-C/X-SAR (Shuttle Imaging Radar-C / X-Band Synthetic Aperture Radar) Explore More
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